With the development of wireless communication technologies and the increasing maturity and commercial use of multiple wireless technologies, high rates achieved by high-bandwidth wireless technologies currently have found more and more favor in operators' eyes. Therefore, many operators begin to deploy wireless networks where multiple modes coexist based on an original single wireless network, such as coexistence of a WiMAX (Worldwide Interoperability for Microwave Access, worldwide interoperability for microwave access) network and a 3G (3rd-generation, 3rd generation mobile communication technology) network, coexistence of an LTE (Long Term Evolution, long term evolution) network and a 3G network, and coexistence of a 3G network and another 3G network. Under this technical background, a multimode terminal that is capable of accessing networks of multiple modes and implementing service switching between the networks of multiple modes has emerged.
However, if existing networks of multiple modes coexist, regardless of whether a multimode switching operation is performed, an IP (Internet Protocol, Internet Protocol) address obtained by a multimode terminal from a network side does not change. For example, when a PC (personal computer, personal computer) accesses the Internet by using a multimode terminal, the multimode terminal acquires a public network IP address from an access network, and the PC acquires a private network address from the multimode terminal to implement network access; in addition, to send a packet of the PC to the Internet, the multimode terminal generally uses the NAT (Network Address Translation, network address translation) technology to translate the packet first. Therefore, the multimode terminal needs to maintain a NAT translation table to ensure that a data packet between the PC and the Internet can be correctly forwarded.
However, in a networking scenario shown in FIG. 1, when a multimode terminal performs network switching, that is, when it switches from a network connected to a Modem (modem) A to a network connected to a Modem B, the multimode terminal needs to switch its route from the Modem A to the Modem B, but a translation NAT table cannot be switched from the Modem A to the Modem B. As a result, a data service cannot continue, that is, the data service is interrupted, resulting in a poor user experience.